Recording data recording method, recording data reproduction method, recording device, reproduction device, and multi-layered optical recording medium

ABSTRACT

The recording data-recording method according to the present invention records recording data encrypted based on a predetermined encryption code on a multilayer optical recording medium comprising two recording layers of a L1 recording layer and a L0 recording layer deposited on at least one side of a substrate. In doing this, the distance between a reference point in the L1 recording layer as a second layer, as counted from an incident direction of a reproduction laser beam or a recording laser beam, and a reference point in the L0 recording layer as a second recording layer, as counted from the incident direction is obtained, and the recording data is encrypted using distance information enabling identification of the obtained distance as the encryption code. This makes it possible to reliably restrict reproduction of recording data from an optical recording medium to which the recording data is copied, while reducing burden on an authorized user.

TECHNICAL FIELD

This invention relates to a recording data-recording method and arecording device, for recording of recording data after encrypting therecording data, a recording data-reproducing method and a reproductiondevice, for decrypting the encrypted recording data and therebyreproducing the recording data, and a multilayer optical recordingmedium having program data recorded thereon for decrypting the encryptedrecording data.

BACKGROUND ART

Today, various types of optical recording media are widely used, whichcapture attention with their capability of recording large amounts ofrecording data. In this case, as the method of protecting recording datafor prevention of unauthorized copying of recording data recorded on theoptical recording media, there are conventionally known a method ofsetting an attribute of recording data e.g. to invisible, a method ofrecording of recording data in a special format, and so forth. However,even if these recording data-protecting methods are employed, recordingdata can be relatively easily copied e.g. by using a personal computer.For this reason, a recording data-protecting method has been devisedwhich protects recording data by recording the same after encryptionbased on a predetermined encryption code, to thereby make it impossiblefor a third party to reproduce (decrypt) the recording data even ifunauthorized copying of an optical recording medium having the recordingdata recorded thereon is carried out. In this recording data-protectingmethod, recording data is recorded on the optical recording medium afteralteration (encryption) of the data structure of the recording dataaccording to a predetermined algorithm e.g. using an encryption code(e.g. a character string consisting of numerals and alphabeticalletters) which can be known only by an authorized user of the recordingdata. This protects the recording data recorded on the optical recordingmedium from unauthorized reproduction by a third party, since theoriginal data of the recording data is made unrecognizable even if thecontents of the recording data are directly viewed using a text editor,a binary editor or the like.

Further, when the encrypted recording data is reproduced by theauthorized user, first, the recording data is decrypted using adedicated decryption program. In doing this, the reproduction deviceprompts the user to input the encryption code according to thedecryption program, and reconstructs (decrypts) the data structure ofthe recording data according to a procedure reverse to the abovepredetermined algorithm using the inputted encryption code. In thisprocess, if an encryption code which is different from the encryptioncode used in encryption of the recording data is inputted, thereproduction device decrypts the recording data using the encryptioncode different from that used in the encryption. Therefore, thedecrypted recording data has a data structure (in a irreproduciblestate) different from that of the recording data before encryption,whereby the recording data is protected from the unauthorizedreproduction by a third party. This enables only the user who can knowthe encryption code used for encryption of the recording data toproperly decrypt the encrypted recording data into the recording databefore encryption and reproduce the recording data.

On the other hand, Japanese Laid-Open Patent Publication (Kokai) No.H07-21697 discloses the technique of inhibiting reproduction ofrecording data recorded in an optical recording medium formed byunauthorized copying (hereinafter referred to as “the copy medium”), byrecording an identification data ID peculiar to the optical recordingmedium in a lead-in area. More specifically, an identification data IDis formed by a combination of letters representative of pointerinformation on pointers specifying recording respective locations ofrecording data recorded on an original optical recording medium(hereinafter referred to as “the original medium”) and authorinformation on authors or the like of the recording data, and theidentification data ID is recorded in a lead-in area together with thepointer information and the author information. In this case, when thiskind of optical recording medium is copied by a general copying method,the various pieces of information stored in the lead-in area are notread out from the original medium to be copied into the copy medium, butpointer information and the like newly generated based on recordinglocations of recording data copied to the copy medium are recorded inthe lead-in area of the copy medium. Therefore, when the original mediumis copied to another optical recording medium by a general copyingmethod, since the identification data ID is not copied to the copymedium, no identification ID exists in the copy medium.

Further, this optical recording medium (original medium) stores aprogram as recording data. The program describes a process that firstdetermines, when it is started after being read out from the opticalrecording medium, whether or not there exists identification data ID inthe lead-in area of the medium to thereby determine whether the opticalrecording medium is an original medium. Therefore, when reproduction ofthe recording data recorded on the copy medium (execution of theprogram) is attempted, since the identification data ID does not existin the lead-in area of the copy medium, it is determined according tothe description of the program that the medium used is the copy medium,so that the reproduction of the recording data thereafter is inhibited.Further, when the original medium is copied by the general copyingmethod, the recording locations of the recording data in the originalmedium are different from those of the corresponding recording data inthe copy medium. Therefore, even if identification data ID is copied tothe lead-in area of a copy medium, the pointer information correspondingto the identification data ID and the pointer information correspondingto the recording locations of the recording data copied to the copymedium do not coincide with each other. For this reason, it isdetermined according to the description of the program that the mediumused is the copy medium, so that the reproduction of the recording datathereafter is inhibited. Thus, the reproduction of the recording datarecorded in the copy medium is inhibited.

DISCLOSURE OF THE INVENTION

The present inventors studied the recording data-protecting methodsdescribed above, and eventually has found out the following problems:According to the recording data-protecting method based on encryption,the reproduction of recording data recorded on an optical recordingmedium by a third party is restricted by recording the recording dataafter encryption thereof based on an encryption code which can be knownonly by an authorized user of the recording data. However, when therecording data is reproduced which is protected (encrypted) by thisrecording data-protecting method, it is necessary to input theencryption code used in encryption to thereby cause the reproductiondevice to decrypt the recording data. For this reason, there arises aproblem that the operation of inputting the encryption code is verytroublesome. Further, according to this recording data-protectingmethod, even if a person is an authorized user, insofar as the user doesnot remember an encryption code, the recording data cannot be decrypted(reproduced). In this case, if a memo of the encryption data is made soas to prevent the encryption data used in encryption from being lost inoblivion, there is a fear of the memo being stolen for use by a thirdparty to decrypt the recording data. Further, when wrong encryption datais inputted by mistake when decrypting the recording data, the recordingdata is prevented from being decrypted into the state before encryption,which makes it impossible to reproduce the recording data. For thisreason, the authorized user is required to accurately memorize theencryption code without taking a memo thereof, which puts a very largeburden on the user.

On the other hand, according to the recording data-protecting methoddisclosed in Japanese Laid-Open Patent Publication (Kokai) No.H07-21697, identification data ID is recorded in the lead-in area whereit is difficult to carry out rewriting and copying, and the program isalso recorded as recording data, which describes the process fordetermining whether the optical recording medium is the original mediumor the copy medium based on whether the identification data ID exists inthe lead-in area. This inhibits the start of the program (reproductionof the recording data) from the copy medium formed by unauthorizedcopying. However, it is technically possible to copy the various piecesof information in the lead-in area to another optical recording medium,which makes it practically meaningless to determine whether the opticalrecording medium is the original medium or the copy medium based onwhether or not the identification data ID exists. Since it ispractically difficult to determine whether the medium is the originalmedium or the copy medium, it is difficult to reliably protect therecording data.

Further, according to this recording data-protecting method, the pointerinformation and the author information are used as contents of theidentification data ID. In this case, as described above, it is possibleto copy the various pieces of information in the lead-in area into thelead-in area of the copy medium, and in addition, it is also technicallypossible to record recording data on the copy medium at recordinglocations made corresponding to those of the original medium. Therefore,the pointer information and author information recorded on the originalmedium and the pointer information and author information recorded onthe copy medium can be easily made identical to each other. Therefore,when these pieces of information and the contents of the identificationdata ID are compared with each other, it is determined that the opticalrecording medium is the original medium in spite of the fact that it isactually the copy medium.

The present invention has been made to solve the above problems, and itis a main object of the invention to provide a recording data-recordingmethod, a recording data-reproducing method, a recording device, areproduction device, and a multilayer optical recording medium, whichare capable of reliably restricting reproduction of recording data froman optical recording medium to which the recording data is copied, whilereducing burden on an authorized user.

The recording data-recording method according to the present inventionis a recording data-recording method for recording of recording dataencrypted based on a predetermined encryption code on a multilayeroptical recording medium comprising N (N is a natural number not smallerthan 2) recording layers deposited on at least on one side of asubstrate, wherein a distance between a first reference point in an M-thone (M is a natural number not larger than N) of the recording layers,as counted from an incident direction of a reproduction laser beam or arecording laser beam, and a second reference point in an L-th one (L isa natural number not larger than N and other than M) of the recordinglayers, as counted from the incident direction is obtained, and therecording data is encrypted using distance information enablingidentification of the obtained distance as the encryption code.

According to the recording data-recording method, the distance betweenthe first reference point in the M-th recording layer, as counted fromthe incident direction of the reproduction laser beam or the recordinglaser beam, and the second reference point in the L-th recording layer,as counted from the incident direction is obtained, and the recordingdata is encrypted using the distance information enabling identificationof the obtained distance as the encryption code. Thus, the distanceinformation which varies with each of multilayer optical recording mediais used as the encryption code, so that even if the recording dataencrypted based on the encryption code is copied to any other multilayeroptical recording medium, distance information (encryption code used fordecryption) in the copy of the multilayer optical recording medium, andthe distance information (encryption code used for encryption) in theoriginal multilayer optical recording medium do not coincide with eachother. As a result, it is possible to restrict normal decryption of anunauthorized copy of the recoding data. Therefore, it is possible toreliably protect recording data (encrypted recording data) recorded onthe original multilayer optical recording medium from unauthorizedreproduction by a third party. Additionally, it is possible to encryptand decrypt the recording data without inputting the encryption code,and hence largely reduce burden on the user.

In this case, it is preferred that the recording data-recording methodwherein an angle of intersection of a first segment passing through oneof the first reference point and the second reference point, and a thirdreference point in a K-th one (K is a natural number not larger than Nand includes a same number equal to M or L) of the recording layers, ascounted from the incident direction, and a second segment passingthrough the first reference point and the second reference point isobtained, and the recording data is encrypted using angle informationenabling identification of the obtained angle as part of the encryptioncode. By virtue of this configuration, when compared with the method ofencrypting recording data based on an encryption code based on thedistance information alone, analysis of encryption of the recording dataand decryption based on the results of analysis are made more difficultto perform, so that it is possible to more reliably protect therecording data from unauthorized reproduction thereof by a third party.

Further, it is preferred that program data is recorded which is read outby a reproduction device, and causes the reproduction device to obtainthe distance between the first reference point and the second referencepoint as the encryption code, and decrypt the encrypted recording databased on the obtained encryption code. Now, the reproduction device inthe present invention includes a single reproduction drive unit, and awhole system comprised of a reproduction drive unit and an electronicterminal unit connected to the reproduction drive unit. By virtue ofthis configuration, insofar a user owns a multilayer optical recordingmedium which has recording data recorded thereon by the recordingdata-recording method according to the present invention, it is possibleto reliably reproduce (decrypt) the recording data encrypted andrecorded on the multilayer optical recording medium.

Further, it is preferred that the program data is recorded in any one ofa data recording area, a lead-in area, and a lead-out area in themultilayer optical recoding medium. By virtue of this configuration, auser who has purchased the multilayer optical recording medium can causethe program data to be recorded only when the recording data is recordedby the data-protecting method, which makes it possible to recordrecording data on each single type of multilayer optical recordingmedium by a desired one of the data-protecting method and the generalmethod. Further, by recording the program data in any of thedata-recording area, the lead-in area, and the lead-out area from whichvarious reproduction devices can reliably read out recorded contents, itis possible to reliably read out the program data using the variousreproduction devices other than the recording device which caused theprogram data to be recorded thereon. This makes it possible to reliablydecrypt the encrypted recording data for reproduction. In this case, byrecording the program data in either the lead-in area or the lead-outarea, it becomes difficult to analyze the program data, so that it ispossible to effectively prevent unauthorized rewriting of the programdata.

Further, it is preferred that the program data is recorded in one of anarea which is first accessed by the reproduction device when themultilayer optical recording medium is loaded, and an area designated byarea information recorded in the area first accessed by the reproductiondevice. By virtue of this configuration, the program data is read outonly by loading the multilayer optical recording medium in thereproduction device, which makes it possible to perform rapidreproduction when the multilayer optical recording medium from which therecording data is to be reproduced is the original medium, and reliablyprotect the recording data when the multilayer optical recording mediumfrom which the recording data is to be reproduced is the copy medium.

Moreover, it is preferred that the program data is recorded as part ofthe encrypted recording data, or part of management information on therecording data. By virtue of this configuration, it becomes moredifficult to analyze the program data, so that it is possible to morereliably prevent unauthorized rewriting of the program data.

The recording data-reproducing method according to the present inventionis a recording data-reproducing method for decrypting and reproducingthe recording data recorded by the recoding data-recording methoddescribed above, wherein the distance between the first reference pointand the second reference point of the multilayer optical recordingmedium on which the recording data is recorded as an object to bereproduced is obtained, and the recording data is decrypted usingdistance information enabling identification of the obtained distance asthe encryption code.

According to this recording data-reproducing method, after obtaining thedistance between the first and second reference points of a multilayeroptical recording medium on which recording data to be reproduced isrecorded, the recording data is decrypted using distance informationenabling identification of the distance, whereby insofar as therecording data to be reproduced is recorded on the original medium, itcan be restored (decrypted) to the data structure identical to thatbefore encryption, and if the recording data to be reproduced isrecorded in the copy medium, it is restored to a data structuredifferent from that before encryption, so that it is possible toreliably protect the recording data recorded on the original medium.

Further, it is preferred that an angle of intersection of the firstsegment and the second segment of the multilayer optical recordingmedium on which the recording data is recorded as the object to bereproduced is obtained, and the recording data is decrypted using angleinformation enabling identification of the obtained angle as part of theencryption code. By virtue of this configuration, also as to recordingdata which is encrypted using the angle information as part of theencryption code, it is possible to allow reproduction of the recordingdata from the original medium while reliably preventing unauthorizedreproduction from the copy medium by a third party.

The recording device according to the present invention is a recordingdevice that is capable of recording the recording data by the recordingdata-recording method described above, comprising a turntable that holdsand rotates the multilayer optical recoding medium, a pickup that emitsthe reproduction laser beam or the recording laser beam to themultilayer optical recording medium held on the turntable, a movingmechanism that moves the pickup along a direction of radius of themultilayer optical recoding medium, and a control section that controlsrotation of the turntable and motion of the pickup by the movingmechanism and executes encryption of the recording data based on theencryption code, wherein the control section causes the pickup to emitthe reproduction laser beam to the M-th recording layer and the L-threcording layer while causing the turntable to rotate and the movingmechanism to move the pickup, calculates the distance between the firstreference point and the second reference point based on a rotationalangle of the turntable and an amount of movement of the pickup by themoving mechanism when the pickup emits the reproduction laser beam tothe first reference point, and a rotational angle of the turntable andan amount of movement of the pickup by the moving mechanism when thepickup emits the reproduction laser beam to the second reference point,and encodes the recording data using distance information enablingidentification of the calculated distance as the encryption code. Here,the control section in the present invention includes a control sectioncontained in a recording drive unit, and a control section of anelectronic terminal unit connected to the recording drive unit.

According to this recording device, there is calculated the distancebetween the first reference point and the second reference point basedon the rotational angle of the turntable and the amount of movement ofthe pickup by the moving mechanism when the pickup emits thereproduction laser beam to the first reference point, and the rotationalangle of the turntable and the amount of movement of the pickup by themoving mechanism when the pickup emits the reproduction laser beam tothe second reference point, and the recording data is encoded usingdistance information enabling identification of the calculated distanceas the encryption code, whereby even if the recording data encryptedbased on the encryption code is copied to another multilayer opticalrecording medium, the distance information of the multilayer opticalrecording medium to which the recording data is copied and the distanceinformation of the original multilayer optical recording medium do notcoincide with each other, so that normal decryption of the illegallycopied recording data can be restricted. Therefore, it is possible toreliably protect the recording data recorded on the original multilayeroptical recording medium from being illegally reproduced by a thirdparty.

The reproduction device according to the present invention is areproduction device that is capable of reading out the recording datarecorded by the recording data-recording method described above, fromthe multilayer optical recording medium to decrypt the recording data,and then reproducing the recoding data, comprising a turntable thatholds and rotates the multilayer optical recoding medium, a pickup thatemits the reproduction laser beam to the multilayer optical recordingmedium held on the turntable, a moving mechanism that moves the pickupalong a direction of radius of the multilayer optical recoding medium, astorage section that stores program data which causes the reproductiondevice to obtain the distance between the first reference point and thesecond reference point as the encryption code, and decrypt the encryptedrecording data based on the obtained encryption code, and a controlsection that controls rotation of the turntable and motion of the pickupby the moving mechanism, as well as obtains the encryption code andexecutes decryption of the recording data based on the obtainedencryption code according to the program data, wherein the controlsection causes the pickup to emit the reproduction laser beam to theM-th recording layer and the L-th recording layer while causing theturntable to rotate and the moving mechanism to move the pickup,calculates the distance between the first reference point and the secondreference point based on a rotational angle of the turntable and anamount of movement of the pickup by the moving mechanism when the pickupemits the reproduction laser beam to the first reference point, and arotational angle of the turntable and an amount of movement of thepickup by the moving mechanism when the pickup emits the reproductionlaser beam to the second reference point, and encodes the recording datausing distance information enabling identification of the calculateddistance as the encryption code. Here, the control section in thepresent invention includes a control section contained in a reproductiondrive unit, and a control section of an electronic terminal connected tothe reproduction drive unit.

According to the reproduction device, there is calculated the distancebetween the first reference point and the second reference point basedon the rotational angle of the turntable and the amount of movement ofthe pickup by the moving mechanism when the pickup emits thereproduction laser beam to the first reference point, and the rotationalangle of the turntable and the amount of movement of the pickup by themoving mechanism when the pickup emits the reproduction laser beam tothe second reference point, and the recording data is encoded usingdistance information enabling identification of the calculated distanceas the encryption code, whereby insofar as the recording data to bereproduced is recorded on the original medium, it is restored to thedata structure before encryption, and if the recording data to bereproduced is recorded in the copy medium, it is restored to a datastructure different from that before encryption, so that it is possibleto reliably protect the recording data recorded on the original medium.

The multilayer optical recording medium according to the presentinvention is a multilayer optical recording medium that is capable ofrecording the recording data by the recording data-recording methoddescribed above, wherein program data is recorded which is read out by areproduction device, and causes the reproduction device to obtain thedistance between the first reference point and the second referencepoint as the encryption code, and decrypt the encrypted recording databased on the obtained encryption code.

According to this multilayer optical recording medium, program data isrecorded which is read out by a reproduction device, and causes thereproduction device to obtain the distance between the first referencepoint and the second reference point as the encryption code, and decryptthe encrypted recording data based on the obtained encryption code,whereby it is possible to make it unnecessary for the user to carry outthe processing of recording the program data, and hence it is possibleto record the recording data promptly by the data-protecting method.

In this case, it is preferred that the program data is recorded in anyone of a data recording area, a lead-in area, and a lead-out area in themultilayer optical recoding medium. By virtue of this configuration, itis possible, for example, to insure the compatibility with ageneral-purpose multilayer optical recording medium in which the userhas written the program data.

Further, it is preferred that the program data is recorded in one of anarea which is first accessed by the reproduction device when themultilayer optical recording medium is loaded, and an area designated byarea information recorded in the area first accessed by the reproductiondevice. By virtue of this configuration, the program data is read outonly by loading the multilayer optical recording medium in thereproduction device, which makes it possible to perform rapidreproduction when the multilayer optical recording medium from which therecording data is to be reproduced is the original medium, and reliablyprotect the recording medium when the multilayer optical recordingmedium from which the recording data is to be reproduced is the copymedium.

Further, it is preferred that the program data is recorded as pre-pits.By virtue of this configuration, it is possible to reliably preventrewriting of the program data. Further, it is possible to make itunnecessary to perform the process of recording the program data on themultilayer optical recording medium, and hence it is possible to providea multilayer optical recording medium which can perform recording ofrecording data by the data-protecting method promptly and easily.Further, the program data need not be stored in the storage section, andhence it is possible to sufficiently reduce the manufacturing costs ofthe recording device.

It should be noted that the present disclosure relates to the subjectmatter included in Japanese Patent Application No. 2002-100750 filed onApr. 3, 2002, and it is apparent that all the disclosures therein areincorporated herein by reference.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing the construction of amultilayer optical recording medium 1 according to an embodiment of theinvention;

FIG. 2 is a conceptual diagram for explaining the positionalrelationship between a L1 recording layer 3 and a L0 recording layer 5of the multilayer optical recording medium 1;

FIG. 3 is a block diagram showing the arrangement of arecording/reproduction device 11 according to the embodiment of thepresent invention, and a personal computer PC;

FIG. 4 is a flowchart of a data recording process 20 executed by therecording/reproduction device 11;

FIG. 5 is a flowchart of a data encrypting process 30 executed by therecording/reproduction device 11;

FIG. 6 is an explanatory view showing the positional relationshipbetween reference points P3 b, P5 b, and P5 a, a distance W, and anangle θ at the time of generation of an encryption code Dc;

FIG. 7 is an explanatory view for explaining a vector V to be identifiedbased on the distance W and the angle θ; and

FIG. 8 is a flowchart of a data reproducing process 40 executed by therecording/reproduction device 11 and the personal computer PC.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a recording data-recording method, a recordingdata-reproducing method, a recording device, a reproduction device, anda multilayer optical recording medium, according to a preferredembodiment of the present invention, will be described with reference tothe accompanying drawings.

First of all, the construction of the multilayer optical recordingmedium 1 will be described with reference to the drawings.

The multilayer optical recording medium 1 shown in FIG. 1 is asingle-sided two-layered rewritable optical recording medium, forexample, and has an L1 recording layer 3, a spacer layer 4, an L0recording layer 5, and a covering layer 6 sequentially deposited in thementioned order on a substrate 2 in the form of a flat plate (e.g. inthe form of a disk), with a mounting central hole H formed through acentral portion thereof. The substrate 2 is made of a resin material,such as a polycarbonate, by injection molding, and a surface thereoftoward the covering layer 6 is formed with fine protrusion/depression,such as helical grooves (guiding grooves) and lands. The L1 recordinglayer 3 is comprised of thin films layered on the fineprotrusion/depression of the substrate, such as a reflective film forreflecting a recording laser beam and a reproduction laser beam (each ofwhich is hereinafter also simply referred to as “the laser beam” when itis not required to make a distinction between the two laser beams), aphase change film whose optical reflectance is changed with a change inan optical constant caused by application of the recording laser beam,and a protective film for protecting the phase change film. The spacerlayer 4 is formed of a light-transmitting resin, and a surface thereoftoward the covering layer 6 is formed with fine protrusion/depression,such as helical grooves and lands. The L0 recording layer 5 is comprisedof thin films layered on the fine protrusion/depression of the spacerlayer 4, such as a phase change film and a protective film. The coveringlayer 6, which is for preventing the layers on the substrate 2 frombeing scratched or damaged, and for adjusting the thickness of the wholemultilayer optical recording medium 1, is made of a light-transmittingresin. In the multilayer optical recording medium 1, the laser beam isapplied in a direction indicated by an arrow X in FIG. 1, wherebyrecording of various digital data on the recording layers 3 and 5 orreading of various digital data from the recording layers 3 and 5 isperformed. It should be noted that in the embodiment of the presentinvention, the L1 recording layer 3 will be described as the M-threcording layer in the present invention, and the L0 recording layer 5as the L-th and K-th recording layers in the present invention, by wayof example.

In the multilayer optical recording medium 1, the L0 recording layer 5that records various digital data (recording data) thereon is comprisedof a lead-in area 5 a defined by a radially innermost portion thereof,and a data-recording area 5 b defined radially outward of the lead-inarea 5 a, and the L1 recording layer 3 that similarly records variousdigital data (recording data) thereon is comprised of a lead-out area 3a defined by a radially innermost portion thereof, and a data-recordingarea 3 b defined radially outward of the lead-out area 3 a. In thiscase, in the lead-in area 5 a, there are recorded management data Dtcomprising at least physical format information on various digital datarecorded on the data-recording areas 5 b and 3 b, FAT (File AllocationTable) data, and location data that designates a recording location ofdata first to be read out when the multilayer optical recording medium 1is loaded in various reproduction devices (e.g. “TOC (Table OfContents)” or “UTOC (User Table Of Contents)”). Further, in thedata-recording areas 5 b and 3 b, there are recorded recording data Dd,Dd, . . . (not only sound data, image data, music data, and text databut also program data of various application software, and applicationdata produced or updated by a user) encrypted through an encryptionprocess, described hereinafter, decryption program data Dp correspondingto program data in the present invention, and so forth. It should benoted that actually, there sometimes exist known areas, such as PCA(Power Calibration Area), TA (Test Area), CA (Count Area), and PMA(Program Memory Area), farther radially inward of the lead-in area 5 a,but detailed description thereof and illustration in figures areomitted.

In this case, in manufacturing the multilayer optical recording medium1, first, the L1 recording layer 3 is formed on the substrate 2 that hasbeen formed by injection molding with fine protrusion/depression (e.g.grooves and lands) thereon. Then, after a light-transmitting resin ise.g. spin-coated on the L1 recording layer 3, the light-transmittingresin is cured with a stamper being placed thereon for forming fineprotrusion/depression, whereby the spacer layer 4 is formed.Subsequently, after separation of the stamper, the L0 recording layer 5is formed on the fine protrusion/depression of the spacer layer 4, and alight-transmitting resin is e.g. spin-coated to cover the L0 recordinglayer 5, and thereafter cured. Thus, the multilayer optical recordingmedium 1 is manufactured. Therefore, as shown in FIG. 2, in themultilayer optical recording medium 1, the center O5 of the L0 recordinglayer 5 (the center of the helical grooves and lands formed on thespacer layer 4) is off-center with respect to the center O3 of the L1recording layer 3 (the center of the helical grooves and lands formed onthe substrate 2) within a range of several tens of μm due todisplacement of a position where the stamper is placed on thelight-transmitting resin during formation of the spacer layer 4.Further, the centers O5 and O3 are also off-center with respect to thecenter O of the multilayer optical recording medium 1 (the center ofmounting central hole H) within a range of several tens of μm due tomisalignment occurring in forming the fine protrusion/depression andmisalignment in forming the mounting central hole H during injectionmolding of the substrate 2. Further, the amount of eccentricity betweenthe centers O5 and O3, and the amounts of eccentricities of the centersO5 and O3 with respect to the center O vary with each of the multilayeroptical recording media 1, 1, . . . It should be noted that in FIG. 2,the amount of displacement between the L1 recording layer 3 and the L0recording layer 5 is shown in an exaggerated manner for ease ofunderstanding of the present invention.

Furthermore, the stamper is placed on the substrate 2, without thehelical fine protrusion/depression of the stamper and the helical fineprotrusion/depression in the L1 recording layer 3, already formed on thesubstrate 2, being completely overlaid upon each other. Therefore, adirection from the center O5 of the L0 recording layer 5 toward thestarting location of the lead-in area 5 a (the radially innermostportion of the lead-in area 5 a: hereinafter also referred to as the“reference point P5 a”) (direction indicated by an arrow A5 a shown inthe figure), and a direction from the center O3 of the L1 recordinglayer 3 toward the terminating location of the lead-out area 3 a (theradially innermost portion of the lead-out area 3 a: hereinafter alsoreferred to as the “reference point P3 a”) (direction indicated by anarrow A3 a shown in the figure) do not necessarily coincide with eachother, and moreover the amount of difference between these directionsvaries with each of the multilayer optical recording media 1, 1, . . .Similarly, a direction from the center O5 of the L0 recording layer 5toward the starting location of the data-recording area 5 b (theradially innermost portion of the data-recording area 5 b: hereinafteralso referred to as the “reference point P5 b”) (direction indicated byan arrow A5 b shown in the figure), and a direction from the center O3of the L1 recording layer 3 toward the terminating location of thedata-recording area 3 b (the radially innermost portion of thedata-recording area 3 b: hereinafter also referred to as the “referencepoint P3 b”) (direction indicated by an arrow A3 b shown in the figure)do not necessarily coincide with each other, and moreover the amount ofdifference between these directions varies with each of the multilayeroptical recording media 1, 1, . . . Accordingly, there are an infinitenumber of combinations of the above “amounts of eccentricities” and the“directions from the center O5 (O3) toward the reference points P5 a andP5 b (reference points P3 a and P3 b)”. Further, even if an attempt ismade to form the L0 recording layer 5 and the L1 recording layer 3 withthe same amounts of eccentricities and the same directions, as a matterof fact, it is very difficult to form them in such a state. Therefore,by using information enabling identification of the “amounts ofeccentricities” and the “directions” as an encryption code, it ispossible to provide an encryption code difficult to duplicate.

Next, a recording/reproduction device 11 and a personal computer PC, forperforming recording of recording data on the multilayer opticalrecording medium 1 and reproduction of the recording data, will bedescribed with reference to FIG. 3.

The recording/reproduction device 11 is e.g. an outboard drive unit thatcan be connected to the personal computer PC or the like, and configuredto be capable of carrying out recording and reading of various digitaldata on and from the multilayer optical recording medium 1. Therecording/reproduction device 11 corresponds to the recording device andthe reproduction device in the present invention, and includes aturntable 12, a pickup 13, a spindle servo 14, a feed servo 15, a focustracking servo 16, a control section 17, and a ROM 18. The turntable 12is configured to be capable of having the multilayer optical recordingmedium 1 placed (chucked, i.e. held) thereon, and rotated together withthe multilayer optical recording medium 1, at a constant linearvelocity, by a spindle motor, not shown, controllably driven by thespindle servo 14.

The pickup 13 is configured to have a laser-emitting section and alaser-receiving section integrally formed with each other. When a laser,not shown, is driven by a laser driver, not shown, under the control ofthe control section 17, the pickup 13 emits a recording laser beam or areproduction laser beam (emitted laser La) to the multilayer opticalrecording medium 1. As a result, recording of a signal on the multilayeroptical recording medium 1, or delivery of an electric signal dependenton the level of a reflected laser Lb from a recorded location of themultilayer optical recording medium 1 is performed. Further, the pickup13 includes an objective lens and a half mirror, neither of which isshown, and the focus tracking servo 16 performs the focus trackingcontrol of the objective lens, whereby the laser beam is focused ontothe L1 recording layer 3 or the L0 recording layer 5 of the multilayeroptical recording medium 1. The pickup 13 is caused to reciprocate bythe feed servo 15 along the direction of the radius of the multilayeroptical recording medium 1 between the inner periphery and the outerperiphery thereof.

The spindle servo 14 controls, under the control of the control section17, the rotation of the turntable 12 such that the linear velocitythereof is constant. The spindle servo 14 delivers a rotation amountsignal Sa dependant on the amount of the rotation of the turntable 12(i.e. the amount of the rotation of the multilayer optical recordingmedium 1) to the control section 17. The feed servo 15 corresponds to amoving mechanism in the present invention, and causes the pickup 13 toreciprocate along the direction of the radius of the multilayer opticalrecording medium 1, as described above. The feed servo 15 delivers amovement amount signal Sb dependant on the amount of movement of thepickup 13 to the control section 17. The control section 17 controls thedriving of the pickup 13, the spindle servo 14, the feed servo 15, andthe focus tracking servo 16, and reads recording data recorded on the L1recording layer 3 or the L0 recording layer 5 based on the electricsignal delivered from the pickup 13. Further, the control section 17calculates the existing position of the pickup 13 based on the rotationamount signal Sa and the movement amount signal Sb delivered from thespindle servo 14 and the feed servo 15, and delivers a position signalSc dependent on the existing position to the personal computer PC. TheROM 18 has the decryption program data Dp recorded thereon, which is tobe recorded on the multilayer optical recording medium 1 when therecording data Dd, Dd, . . . are recorded on the multilayer opticalrecording medium 1 by a data-protecting method, as will be describedhereinafter.

In this case, the decryption program data Dp is data in which isdescribed a program for decrypting the recording data Dd, Dd, . . .encrypted through a data-encrypting process 30, described hereinafter,by generating an encryption code Dc1 following the same procedure asfollowed when an encryption code Dc is generated during encryption ofthe recording data Dd, and decrypting the recording data Dd using theencryption code Dc1 according to an algorithm reverse in procedure to analgorithm used during the encryption. The decryption program data Dp isrecorded in a file format readable by various types of personalcomputers, and contains a description for being automatically started bythe personal computers immediately after completion of reading thereof.More specifically, the decryption program data Dp is comprised ofexecutable files, such as AUTORUN.EXE, various batch files, and variousmodule files that can be started by the executable files and the batchfiles.

The personal computer PC performs overall control of recording andreading of the recording data Dd, Dd, . . . and the like via therecording/reproduction device 11, and executes a predetermineddecryption process according to a decryption program (contents ofdescription of the decryption program data Dp) during reproduction ofthe recording data Dd, as described hereinafter.

Next, a description will be given of a recording method for recordingthe recording data Dd, Dd, . . . on the multilayer optical recordingmedium 1, which is unused, and a reproduction method for reproducing therecording data Dd, Dd, . . . recorded on the multilayer opticalrecording medium 1, with reference to the drawings. It should be notedthat the following description of the embodiment of the presentinvention is given assuming that the reference point P3 b is the firstreference point in the present invention, the reference point P5 b isthe second reference point in the present invention, and the referencepoint P5 a is the third reference point in the present invention.

First, a data-recording process 20 carried out by therecording/reproduction device 11 and the personal computer PC will bedescribed with reference to FIG. 4. In the recording/reproduction device11, when a multilayer optical recording medium 1 is inserted into adisk-inserting section, not shown, the control section 17 controllablydrives the spindle servo 14 to cause rotation of the turntable 12. Then,the control section 17 controllably drives the feed servo 15 to therebymove the pickup 13 to the radially innermost portion of the multilayeroptical recording medium 1, and causes the reproduction laser beam(emitted laser La) to be emitted to the multilayer optical recordingmedium 1, while controllably driving the focus tracking servo 16. Inthis case, in the multilayer optical recording medium 1, variousinformation items (in this case, these “various information items” areintended to mean not information directly used by the user, butinformation used by various recording devices or reproduction devices)including e.g. disk-type information that the optical recording mediumis a rewritable (or write-once) medium of a single-sided two-layeredtype are recorded in the lead-in area 5 a, an area farther radiallyinward of the lead-in area 5 a, and the like. Therefore, the controlsection 17 determines that the multilayer optical recording medium 1 isa single-sided two-layered rewritable optical recording medium.

Then, the control section 17 controllably drives the feed servo 15 tomove the pickup 13 to the lead-in area 5 a, and determines whether ornot the multilayer optical recording medium 1 is a medium havingrecording data recorded thereon by the data-protecting method, based onwhether or not the decryption program data Dp is recorded in thedata-recording area 5 b (whether or not the management data Dtconcerning the decryption program data Dp exists) (step 21). In thiscase, in the multilayer optical recording medium 1 on which are recordedrecording data Dd, Dd, . . . encrypted through the data-encryptingprocess 30, described hereinafter, (the multilayer optical recordingmedium 1 having recording data recorded thereon by the data-protectingmethod), the decryption program data Dp is recorded in the starting areaof the data-recording area 5 b. Therefore, when the decryption programdata Dp exists, the control section 17 determines that the multilayeroptical recording medium 1 is a medium having recording data recordedthereon by the data-protecting method, and immediately executes thedata-encrypting process 30 on recording data Dd, Dd, . . . to berecorded on the multilayer optical recording medium 1. On the otherhand, in the data-recording area 5 b of the multilayer optical recordingmedium 1, which is unused, is in a state not having the decryptionprogram data Dp and recording data Dd recorded thereon. Accordingly,when the management data Dt concerning the decryption program data Dpdoes not exist in the lead-in area 5 a, the control section 17determines that the multilayer optical recording medium 1 is not amedium having recording data recorded thereon by the data-protectingmethod.

Subsequently, the control section 17 causes a selection screen to bedisplayed on a monitor of the personal computer PC, for allowing theuser to select a method of recording of recording data on the multilayeroptical recording medium 1, and prompts the user to select either of thedata-protecting method and a normal recording method (step 22). In doingthis, when the normal recording method is selected by the user, thecontrol section 17 causes recording data Dd outputted from the personalcomputer PC to be recorded in the data-recording areas 3 b and 5 b ofthe multilayer optical recording medium 1 (step 23), and when all therecording data Dd, Dd, . . . have been recorded, causes the managementdata Dt indicating e.g. the respective recording locations of therecording data Dd, Dd, . . . to be recorded in the lead-in area 5 a(step 24). Thus, recording data Dd, Dd, . . . (unencrypted recordingdata Dd) allowing reproduction thereof by all users including theauthorized user are recorded on the multilayer optical recording medium1. On the other hand, when the data-protecting method is selected in thestep 22, the control section 17 reads out the decryption program data Dpfrom the ROM 18, and causes the same to be recorded on the startingportion of the data-recording area 5 b (step 25). Then, the controlsection 17 causes FAT data concerning a recording location of thedecryption program data Dp, location data designating the recordinglocation of the decryption program data Dp as first data to be read outwhen the multilayer optical recording medium 1 is loaded in variousreproduction devices including the recording/reproduction device 11, andso forth, to be recorded as part of the management data Dt e.g. in thelead-in area 5 a (step 26).

Next, the control section 17 executes the data-encrypting process 30shown in FIG. 5 on the recording data Dd outputted from the personalcomputer PC. In the data-encrypting process 30, first, the controlsection 17 identifies the terminating location (reference point P3 b) ofthe data-recording area 3 b, and the starting location (reference pointP5 b) of the data-recording area 5 b, based on the rotation amountsignal Sa and the movement amount signal Sb delivered from the spindleservo 14 and the feed servo 15 (step 31). More specifically, the controlsection 17 identifies the location of the reference point P3 b based onthe rotation amount signal Sa and the movement amount signal Sbdelivered when the pickup 13 has accessed the reference point P3 b, andidentifies the location of the reference point P5 b based on therotation amount signal Sa and the movement amount signal Sb deliveredwhen the pickup 13 has accessed the reference point P5 b. Then, thecontrol section 17 calculates a distance W between the identifiedreference points P3 b and P5 b in plan view (see FIG. 6) (step 32). Inthis case, a three-dimensional distance including a thickness betweenthe L1 recording layer 3 and the L0 recording layer 5 may be determined.Then, similarly to the method of identifying the reference points P3 band P5 b, the control section 17 identifies the starting location(reference point P5 a) of the lead-in area 5 a based on the rotationamount signal Sa and the movement amount signal Sb (step 33). Next, thecontrol section 17 calculates an angle θ of intersection of a segment W1passing through the reference points P3 b and P5 b, and a segment W2passing through the reference points P5 b and P5 a (see FIG. 6) (step34).

In this case, as described hereinabove, the positional relationshipbetween the reference points P3 b, P5 a, and P5 b varies with each ofthe multilayer optical recording media 1, 1 . . . and hence the distanceW between the reference points P3 b and P5 b and the angle θ ofintersection of the segments W1 and W2 vary with each of the multilayeroptical recording media 1, 1 . . . Further, since the locations of thereference points P3 b, P5 a, and P5 b are not changed due to therecording or reproduction of the recording data Dd, the distance W andthe angle θ determined from the same multilayer optical recording medium1 always have the same values. In this case, since the mounting centralhole H is formed to be slightly larger in diameter than the chuck, notshown, of the turntable 12, the positional relationship between thecenter of the turntable 12 and the center O of the multilayer opticalrecording medium 1 undergoes slight variation whenever the multilayeroptical recording medium 1 is loaded. However, although the amount ofthe displacement (the amount of displacement caused by chucking)presents a problem for identifying the reference points P3 b, P5 a, andP5 b individually, the amount of the displacement is cancelled out whenthe distance W and the angle θ are calculated (measured) based on therelative positional relationship between the reference points P3 b, P5a, and P5 b, and hence the result of the measurement is not adverselyaffected by the amount of the displacement. Therefore, information onthe distance W and the angle θ is used as information peculiar to themultilayer optical recording medium 1. In this case, as shown in FIG. 7,the distance W and the angle θ are represented as a vector V whose axisis the segment W2, whose base point is the reference point P5 b, whoselength (scalar amount) is W, and whose direction is the angle θ.Therefore, in the recording/reproduction device 11, the control section17 generates an encryption code Dc peculiar to the multilayer opticalrecording medium 1, using numerical information representing the vectorV as the distance information and angle information in the presentinvention (step 35).

Next, the control section 17 alters (encrypts) the data structure of therecording data Dd using the generated encryption code Dc, according to apredetermined encryption algorithm (step 36). In this case, therecording data Dd encrypted based on the encryption code Dc is in astate made unrecognizable even if an attempt is made to directly viewthe contents of the recording data, whereby it is protected fromunauthorized reproduction by a third party. Next, the control section 17determines whether or not there exists another recording data Dd to beencrypted (step 37), and when all the recording data Dd, Dd, . . . havebeen encrypted, it completes the data-encrypting process 30.Subsequently, the control section 17 returns to the data-recordingprocess 20 shown in FIG. 4 to cause the recording data Dd, Dd, . . .encrypted by the data-encrypting process 30 to be recorded in thedata-recording areas 3 b and 5 b (step 23). Further, when all therecording data Dd, Dd, . . . have been recorded, the control section 17performs recording (write-once) of e.g. respective recording locationsof the recording data Dd, Dd, . . . , as part of the management data Dt,in the lead-in area 5 a or the like (step 24). Thus, the recording dataDd, Dd, . . . are recorded on the multilayer optical recording medium 1by the data-protecting method. In the following, the multilayer opticalrecording medium 1 having the recording data Dd, Dd, . . . recordedthereon by the data-protecting method is also referred to as the“original multilayer optical recording medium 1”.

Next, a data-reproducing process 40 for reproducing the recording dataDd, Dd, . . . recorded in the multilayer optical recording medium 1using the recording/reproduction device 11 by the data-protecting methodwill be described with reference to drawings.

When the multilayer optical recording medium 1, on which are recordedthe recording data Dd, Dd, . . . encrypted through the data-encryptingprocess 30 described above and the decryption program data Dp, is loadedin the recording/reproduction device 11 (or any otherrecording/reproduction device), the data-reproducing process 40 shown inFIG. 8 is executed. In the data-reproducing process 40, when themultilayer optical recording medium 1 is inserted, first, the controlsection 17 reads out the management data Dt from the lead-in area 5 a(step 41). In this case, on the management data Dt, there is recordedthe location data designating the recording location (in this case, thestart of the data-recording area 5 b) of the decryption program data Dpas first data to be read out. Therefore, the control section 17 readsout the decryption program data Dp from the head of the data-recordingarea 5 b in accordance with the designation (step 42), and transfers thedecryption program data Dp to the personal computer PC. In this case,since the decryption program data Dp is formed in the file formatautomatically started immediately after completion of reading of thedecryption program data Dp, the personal computer PC automaticallyexecutes the contents of description of the decryption program data Dpread out via the recording/reproduction device 11 (starts the decryptionprogram).

Then, the personal computer PC identifies, according to the descriptionof the decryption program data Dp, the locations of the reference pointsP3 b and P5 b of the multilayer optical recording medium 1 loaded in therecording/reproduction device 11. More specifically, first, the personalcomputer PC requests the recording/reproduction device 11 to deliver theposition signal Sc. The control section 17 of the recording/reproductiondevice 11 identifies, in response to the request, the location of thereference point P3 b based on the rotation amount signal Sa and themovement amount signal Sb delivered when the pickup 13 has accessed thereference point P3 b, and identifies the location of the reference pointP5 b based on the rotation amount signal Sa and the movement amountsignal Sb delivered when the pickup 13 has accessed the reference pointP5 b. Next, the control section 17 delivers the position signal Scindicating the respective locations of the identified reference pointsP3 b and P5 b to the personal computer PC. The personal computer PCidentifies the locations of the reference points P3 b and P5 b based onthe delivered position signal Sc (step 43), and then calculates thedistance W between the identified reference points P3 b and P5 b (step44). Subsequently, the personal computer PC identifies the location ofthe reference point P5 a based on the position signal Sc, similarly tothe identification of the reference points P3 b and P5 b (step 45).Then, the personal computer PC calculates the angle θ of intersection ofthe segment W1 passing through the reference points P3 b and P5 b andthe segment W2 passing through the reference points P5 b and P5 a (step46). After that, the personal computer PC generates numericalinformation representative of the vector V defined by the calculateddistance W and angle θ as the encryption code Dc1 (step 47).

Next, the personal computer PC reads out the recording data Dd from thedata-recording area 5 b of the multilayer optical recording medium 1loaded in the recording/reproduction device 11 (step 48). Then, thepersonal computer PC reconstructs the data structure of the recordingdata Dd (decrypts the recording data Dd) according to a predeterminedalgorithm (reverse in procedure to the encryption algorithm used in thedata-encrypting process 30) in accordance with the contents ofdescription of the decryption program data Dp, using the encryption codeDc1 generated in the step 47 (step 49). In doing this, if a copy medium,which has the recording data Dd, Dd . . . , and the decryption programdata Dp copied thereon from the original multilayer optical recordingmedium 1, is loaded in the recording/reproduction device 11, thereference points P3 b, P5 b, P5 a used as the basis for generation ofthe encryption code Dc1 are formed at locations different from those ofthe original multilayer optical recording medium 1, so that theencryption code Dc generated based on the reference points P3 b, P5 b,and P5 a recorded on the original multilayer optical recording medium 1(encryption code Dc used in encrypting the recording data Dd), and theencryption code Dc1 generated based on the reference points P3 b, P5 b,and P5 a in the multilayer optical recording medium 1 as the copy mediumare different from each other. Accordingly, when the recording data Ddencrypted based on the encryption code Dc is decrypted based on theencryption code Dc1, the decrypted recording data Dd is largelydifferent in data structure from the recording data Dd unencrypted. As aresult, the decrypted recording data Dd cannot be normally reproduced,and even if the contents of the recording data are directly viewed byvarious types of editors, they are completely illegible. This makes itpossible to reliably restrict unauthorized reproduction of the recordingdata Dd, Dd, . . . recorded on the original multilayer optical recordingmedium 1 (reproduction of the recording data Dd, Dd, . . . from the copyof the multilayer optical recording medium 1).

On the other hand, in the same multilayer optical recording medium 1,the reference points P3 b, P5 b, and P5 a used as the basis forgeneration of the encryption codes Dc and Dc1 are fixed, and thedistance W and the angle θ calculated based thereon are the valuespeculiar to the multilayer optical recording medium 1. Hence, theencryption code Dc (Dc1) generated based on the reference points P3 b,P5 b, and P5 a in the original multilayer optical recording medium 1always has the same value, even if the encryption code Dc (Dc1) isgenerated by any reproduction device and in any fashion. Therefore, whenthe original multilayer optical recording medium 1 is loaded in therecording/reproduction device 11, the encryption code Dc1 and theencryption code Dc have the same value. This means that when therecording data Dd encrypted based on the encryption code Dc is decryptedbased on the encryption code Dc1, the decrypted recording data Dd hasthe same data structure as that of the recording data Dd beforeencryption. This makes it possible to reproduce the recording data Ddread out from the multilayer optical recording medium 1. After that, thecontrol section 17 determines whether or not there exists any otherrecording data Dd, Dd, . . . to be decrypted (step 50), and whendecryption of all the recording data Dd, Dd, . . . has been completed,the control section 17 reproduces the recording data Dd, Dd, . . . (step51).

In this case, also when the multilayer optical recording medium 1 isloaded in any other arbitrary reproduction device (orrecording/reproduction device) in place of the personal computer PC andthe recording/reproduction device 11 used in recording encryptedrecording data Dd on the multilayer optical recording medium 1, thedata-reproducing process 40 is carried out by the reproduction device(or recording/reproduction device). As a result, reproduction of therecording data Dd, Dd, . . . , for example, from an unauthorized copy ofthe multilayer optical recording medium 1 is inhibited, whereby therecording data Dd, Dd, . . . recorded on the original multilayer opticalrecording medium 1 are protected.

As described hereinabove, according to the recording/reproduction device11, when recording data Dd is recorded on the multilayer opticalrecording medium 1 by the data-protecting method, the recording data Ddis encrypted using the peculiar encryption code Dc generated based onthe reference points P3 b, P5 b, and P5 a in the original multilayeroptical recording medium 1, and not only the decryption program data Dpbut also the management data Dt designating the decryption program dataDp to be read first is recorded, whereby when the multilayer opticalrecording medium 1 is reproduced, the recording data Dd is decrypted inaccordance with the contents of description of the decryption programdata Dp, using the encryption code Dc1 generated based on the referencepoints P3 b, P5 b, and P5 a in the multilayer optical recording medium1. Accordingly, in a multilayer optical recording medium 1 (copy medium)different in the positional relationship between the reference points P3b, P5 b, and P5 a from that of the original multilayer optical recordingmedium 1, normal decryption of the recording data Dd is not executed, sothat it is possible to effectively inhibit reproduction of the recordingdata Dd from a multilayer optical recording medium 1 to which therecording data Dd has been illegally copied from the original multilayeroptical recording medium 1. In this case, although in the conventionalrecording data-protecting method based on the encryption, when recordingdata is decrypted, the user is prompted to input an encryption code usedin encrypting the recording data, in the present recordingdata-recording method (recording data-protecting method) using therecording/reproduction device 11, the positional relationship (numericalinformation indicative of the vector V) between the reference points P3b, P5 b, and P5 a in the multilayer optical recording medium 1, whichhas recording data Dd to be protected recorded thereon, is used as theencryption code Dc. Therefore, the user need not input an encryptioncode either during encryption or during decryption of recording data Dd.This makes it unnecessary for the user to memorize the encryption code,thereby making it possible to record (encrypt) and reproduce (decrypt)recording data Dd reliably and easily, only by selecting thedata-protecting method for recording the recording data Dd when it isrecorded.

Further, according to the recording/reproduction device 11, by recordingthe decryption program data Dp in the data-recording area 5 b, when themultilayer optical recording medium 1 having recording data recordedthereon by the data-protecting method is recorded on another multilayeroptical recording medium 1 by a general copying method, the decryptionprogram data Dp is copied on the data-recording area 5 b of a copymedium. Therefore, when the copy medium is reproduced, the recordingdata Dd is decrypted according to the description of the decryptionprogram data Dp. In the process, as described hereinbefore, recordingdata Dd largely different in data structure from the recording data Ddbefore encryption is generated. This makes it impossible to properlyreproduce the recording data Dd, thereby making it possible to reliablyprotect the recording data Dd recorded on the original multilayeroptical recording medium 1. In this case, by recording the decryptionprogram data Dp in the data-recording area 5 b from which various typesof reproduction devices can reliably read out recording data Dd and thelike, the decryption program data Dp can be reliably read out from theoriginal multilayer optical recording medium 1 by various types ofreproduction devices other than the recording/reproduction device (therecording/reproduction device 11 in this case) used in recording thedecryption program data Dp on the multilayer optical recording medium 1.This makes it possible to reliably decrypt and reproduce the encryptedrecording data Dd, Dd, . . . .

It should be noted that the present invention is by no means limited tothe aforementioned embodiment but it can be modified as required. Forexample, although in the above-described embodiment of the presentinvention, the description has been given of an example in which thedecryption program data Dp is recorded on an unused multilayer opticalrecording medium 1 when recording data Dd is recorded by thedata-protecting method, this is not limitative, but it is also possibleto record the decryption program data Dp in advance on each multilayeroptical recording medium 1, 1, . . . e.g. as pre-pits, when themultilayer optical recording media are manufactured. According to thismethod, it is unnecessary not only to write the decryption program dataDp during recording of recording data Dd but also to have the decryptionprogram data Dp recorded in advance on a recording device, whereby it ispossible to increase the speed of recording processing and reduce themanufacturing costs of the recording device. This makes it possible toprovide the user with a multilayer optical recording medium 1 capable ofeffectively protecting recording data. Further, it is also possible tostore the decryption program data Dp in advance in various reproductiondevices instead of recording the same on the multilayer opticalrecording medium 1 as described in the embodiment of the presentinvention. In this case, there is no need to record the decryptionprogram data Dp on the multilayer optical recording medium 1 (includinga case where the decryption program data Dp is recorded during recordingof recording data as well as a case where the decryption program data Dpis recorded during manufacturing of the multilayer optical recordingmedium 1), and further it is possible to record a larger amount ofrecording data Dd, Dd, . . . on the multilayer optical recording medium1, by the amount required for recording the decryption program data Dp.

Furthermore, although in the above-described embodiment of the presentinvention, the description has been given of an example in whichrecording data Dd is encrypted according to the predetermined encryptionalgorithm using the encryption code Dc, the encryption algorithm is notlimited to one kind of algorithm, and it is possible to make analysis ofencrypted recording data Dd more difficult by changing the algorithm foreach of multilayer optical recording media 1, 1, . . . In this case, bychanging an algorithm (reverse in procedure to an encryption algorithm)described in decryption program data Dp according to a change in theencryption algorithm, it is possible to reliably decrypt encryptedrecording data Dd while making it difficult for a third party to analyzethe encrypted recording data Dd.

Further, although in the above-described embodiment, the description hasbeen given of an example in which the encryption code Dc is generatedbased on the starting location (reference point P5 b) of thedata-recording area 5 b, the terminating location (reference point P3 b)of the data-recording area 3 b, and the starting location (referencepoint P5 a) of the lead-in area 5 a, the first, second, and thirdreference points in the present invention are not limited to thestarting location and the terminating location of the data-recordingareas, and the starting location of the lead-in area. For example, theencryption code Dc can be generated based on arbitrary reference pointsin the multilayer optical recording medium 1, such as the center O3 ofthe L1 recording area 3, the center O5 of the L0 recording area 5, theterminating location (reference point P3 a) of the lead-out area 3 a,the terminating location of the data-recording area 3 b, and thestarting location of the data-recording area 5 b, and arbitraryreference points exclusively defined for manufacturing the multilayeroptical recording medium 1. Furthermore, although in the above-describedembodiment, the description has been given of an example in which theencryption code Dc is generated based on the distance W between thereference points P3 b and P5 b, and the angle θ of intersection of thesegments W1 and W2, this is not limitative, but the encryption code Dcmay be generated based only on distance information enablingidentification of the distance W. In such a case as well, the distance Wbetween the reference points P3 b and P5 b varies with each of themultilayer optical recording media 1, 1 . . . , and hence it is possibleto effectively inhibit reproduction of recording data Dd from a copy ofthe multilayer optical recording medium 1, similarly to the encryptioncode Dc generated based on the segment W1 and the angle θ.

Further, although in the above-described embodiment of the presentinvention, the description has been given of an example in which all therecording data Dd, Dd, . . . recorded on the multilayer opticalrecording medium 1 are encrypted by using the encryption code Dc, thisis not limitative, but it is possible, for example, to prompt the userto arbitrarily select recording data Dd, Dd, . . . which needs to beencrypted, to thereby encrypt only selected recording data Dd, Dd, . . .for recording. In doing this, by recording information enablingidentification of either or both of recording locations of the encryptedrecording data Dd, Dd . . . and recording locations of recording dataDd, Dd, . . . recorded without being encrypted, as part of themanagement data Dt, even if both types of recording data, i.e. encryptedrecording data Dd, Dd . . . and unencrypted recording data Dd, Dd, . . .are recorded in a mixed manner on one multilayer optical recordingmedium 1, it is possible to reproduce both types of recording data Dd,Dd, . . . reliably and easily. In this case, for example, by dividingthe data-recording areas 5 b and 3 b of the multilayer optical recordingmedium 1 into a recording area for recording the encrypted recordingdata Dd, and a recording area for recording the unencrypted recordingdata Dd (e.g. setting the data-recording area 5 b to the recording areafor recording the encrypted recording data Dd, and the data-recordingarea 3 b to the recording area for recording the unencrypted recordingdata Dd), it is possible to record and reproduce both types of recordingdata Dd, Dd, . . . easily.

Further, although in the above-described embodiment of the presentinvention, the description has been given of the rewritable multilayeroptical recording medium 1 including the L1 recording layer 3 and the L0recording layer 5 both having a phase change film, this is notlimitative, but the present invention can also be effectively applied toa write-once multilayer optical recording medium including recordinglayers made of various inorganic materials and organic dye-basedmaterials. Furthermore, the number of recording layers of the multilayeroptical recording medium (N recording layers, in the present invention)is not limited to the two of the L1 recording layer 3 and the L0recording layer 5 described in the aforementioned embodiment, but thepresent invention can also be applied to a multilayer optical recordingmedium including three or more recording layers. Further, the recordinglocation of the decryption program data Dp is not limited to thedata-recording area 5 b described in the above embodiment, but thedecryption program data Dp can be recorded in a desired area which canbe accessed by the reproduction device. Furthermore, although in theabove-described embodiment, the description has been given of an examplein which the ROM 18 is provided in the recording/reproduction device 11,and the decryption program data Dp is read out from the ROM 18 andrecorded on the multilayer optical recording medium 1, the location forstoring the decryption program data Dp is not limited to therecording/reproduction device 11, but the decryption program data Dp maybe recorded in advance on a hard disk of the personal computer PC,whereby the data Dp may be caused to be transmitted from the personalcomputer PC and recorded on the multilayer optical recording medium 1when recording data Dp is recorded by the data-protecting method (whenthe data-recording process 20 is carried out).

Further, although in the above-described embodiment, the description hasbeen given of an example in which the encryption process and thedecryption process is carried out in accordance with the contents ofdescription of the decryption program data Dp on the personal computerPC, this is not limitative, but for example, it is also possible toproduce a decryption program that is executable in therecording/reproduction device 11 and record decryption program data ofthe decryption program on the multilayer optical recording medium 1.Furthermore, although in the above-described embodiment, the descriptionhas been given of the recording/reproduction device 11 which is anoutboard drive unit capable of being connected to the personal computerPC, by way of example, this not limitative, but the present inventioncan be applied to various types of recording devices, such as a built-indrive capable of being contained in the personal computer PC, an AVrecording/reproduction device capable of recording and reproducing videoimages and music by the device alone, and a CD recorder capable ofproducing and reproducing music CD-R by the device alone.

INDUSTRIAL APPLICABILITY

As described heretofore, according to the recording data-recordingmethod, the distance between a first reference point in an M-threcording layer, as counted from an incident direction of a reproductionlaser beam or a recording laser beam, and a second reference point in anL-th recording layer, as counted from the incident direction isobtained, and recording data is encrypted using distance informationenabling identification of the obtained distance as an encryption code.Thus, the distance information which varies with each of multilayeroptical recording media is used as an encryption code, so that even ifthe recording data encrypted based on the encryption code is copied toany other multilayer optical recording medium, distance information(encryption code used for decryption) in the copy of the multilayeroptical recording medium, and distance information (encryption code usedfor encryption) in the original multilayer optical recording medium donot coincide with each other. As a result, it is possible to restrictnormal decryption of an unauthorized copy of the recoding data.Therefore, it is possible to reliably protect recording data (encryptedrecording data) recorded on the original multilayer optical recordingmedium from unauthorized reproduction by a third party. Additionally, itis possible to encrypt and decrypt the recording data without inputtingthe encryption code. This makes it possible to realize a recordingdata-recording method which is capable of reliably restrictingreproduction of the recording data from the copy of the opticalrecording medium while reducing burden on the authorized user.

1. A recording data-recording method for recording of recording dataencrypted based on a predetermined encryption code on a multilayeroptical recording medium comprising N (N is a natural number not smallerthan 2) recording layers deposited on at least on one side of asubstrate, wherein a distance between a first reference point in an M-thone (M is a natural number not larger than N) of the recording layers,as counted from an incident direction of a reproduction laser beam or arecording laser beam, and a second reference point in an L-th one (L isa natural number not larger than N and other than M) of the recordinglayers, as counted from the incident direction is obtained, and therecording data is encrypted using distance information enablingidentification of the obtained distance as the encryption code.
 2. Therecording data-recording method as claimed in claim 1, wherein an angleof intersection of a first segment passing through one of the firstreference point and the second reference point, and a third referencepoint in a K-th one (K is a natural number not larger than N andincludes a same number equal to M or L) of the recording layers, ascounted from the incident direction, and a second segment passingthrough the first reference point and the second reference point isobtained, and the recording data is encrypted using angle informationenabling identification of the obtained angle as part of the encryptioncode.
 3. The recording data-recording method as claimed in claim 1,wherein program data is recorded which is read out by a reproductiondevice, and causes the reproduction device to obtain the distancebetween the first reference point and the second reference point as theencryption code, and decrypt the encrypted recording data based on theobtained encryption code.
 4. The recording data-recording method asclaimed in claim 2, wherein program data is recorded which is read outby a reproduction device, and causes the reproduction device to obtainthe distance between the first reference point and the second referencepoint as the encryption code, and decrypt the encrypted recording databased on the obtained encryption code.
 5. The recording data-recordingmethod as claimed in claim 3, wherein the program data is recorded inany one of a data recording area, a lead-in area, and a lead-out area inthe multilayer optical recoding medium.
 6. The recording data-recordingmethod as claimed in claim 4, wherein the program data is recorded inany one of a data recording area, a lead-in area, and a lead-out area inthe multilayer optical recoding medium.
 7. The recording data-recordingmethod as claimed in claim 3, wherein the program data is recorded inone of an area which is first accessed by the reproduction device whenthe multilayer optical recording medium is loaded, and an areadesignated by area information recorded in the area first accessed bythe reproduction device.
 8. The recording data-recording method asclaimed in claim 5, wherein the program data is recorded in one of anarea which is first accessed by the reproduction device when themultilayer optical recording medium is loaded, and an area designated byarea information recorded in the area first accessed by the reproductiondevice.
 9. The recording data-recording method as claimed in claim 3,wherein the program data is recorded as part of the encrypted recordingdata, or part of management information on the recording data.
 10. Therecording data-recording method as claimed in claim 5, wherein theprogram data is recorded as part of the encrypted recording data, orpart of management information on the recording data.
 11. The recordingdata-recording method as claimed in claim 7, wherein the program data isrecorded as part of the encrypted recording data, or part of managementinformation on the recording data.
 12. A recording data-reproducingmethod for decrypting and reproducing the recording data recorded by therecoding data-recording method claimed in claim 1, wherein the distancebetween the first reference point and the second reference point of themultilayer optical recording medium on which the recording data isrecorded as an object to be reproduced is obtained, and the recordingdata is decrypted using distance information enabling identification ofthe obtained distance as the encryption code.
 13. The recordingdata-reproducing method as claimed in claim 12, wherein an angle ofintersection of the first segment and the second segment of themultilayer optical recording medium on which the recording data isrecorded as the object to be reproduced is obtained, and the recordingdata is decrypted using angle information enabling identification of theobtained angle as part of the encryption code.
 14. A recording devicethat is capable of recording the recording data by the recordingdata-recording method claimed in claim 1 comprising: a turntable thatholds and rotates the multilayer optical recoding medium, a pickup thatemits the reproduction laser beam or the recording laser beam to themultilayer optical recording medium held on said turntable, a movingmechanism that moves said pickup along a direction of radius of themultilayer optical recoding medium, and a control section that controlsrotation of said turntable and motion of said pickup by said movingmechanism and executes encryption of the recording data based on theencryption code, wherein said control section causes said pickup to emitthe reproduction laser beam to the M-th recording layer and the L-threcording layer while causing said turntable to rotate and said movingmechanism to move said pickup, calculates the distance between the firstreference point and the second reference point based on a rotationalangle of said turntable and an amount of movement of said pickup by saidmoving mechanism when said pickup emits the reproduction laser beam tothe first reference point, and a rotational angle of said turntable andan amount of movement of said pickup by said moving mechanism when saidpickup emits the reproduction laser beam to the second reference point,and encodes the recording data using distance information enablingidentification of the calculated distance as the encryption code.
 15. Areproduction device that is capable of reading out the recording datarecorded by the recording data-recording method claimed in claim 1, fromthe multilayer optical recording medium to decrypt the recording data,and then reproducing the recoding data, comprising: a turntable thatholds and rotates the multilayer optical recoding medium, a pickup thatemits the reproduction laser beam to the multilayer optical recordingmedium held on said turntable, a moving mechanism that moves said pickupalong a direction of radius of the multilayer optical recoding medium, astorage section that stores program data which causes the reproductiondevice to obtain the distance between the first reference point and thesecond reference point as the encryption code, and decrypt the encryptedrecording data based on the obtained encryption code, and a controlsection that controls rotation of said turntable and motion of saidpickup by said moving mechanism, as well as obtains the encryption codeand executes decryption of the recording data based on the obtainedencryption code according to the program data, wherein said controlsection causes said pickup to emit the reproduction laser beam to theM-th recording layer and the L-th recording layer while causing saidturntable to rotate and said moving mechanism to move said pickup,calculates the distance between the first reference point and the secondreference point based on a rotational angle of said turntable and anamount of movement of said pickup by said moving mechanism when saidpickup emits the reproduction laser beam to the first reference point,and a rotational angle of said turntable and an amount of movement ofsaid pickup by said moving mechanism when said pickup emits thereproduction laser beam to the second reference point, and encodes therecording data using distance information enabling identification of thecalculated distance as the encryption code.
 16. A multilayer opticalrecording medium that is capable of recording the recording data by therecording data-recording method claimed in claim 1, wherein program datais recorded which is read out by a reproduction wdevice, and causes thereproduction device to obtain the distance between the first referencepoint and the second reference point as the encryption code, and decryptthe encrypted recording data based on the obtained encryption code. 17.The multilayer optical recording medium as claimed in claim 16, whereinthe program data is recorded in any one of a data recording area, alead-in area, and a lead-out area in the multilayer optical recodingmedium.
 18. The multilayer optical recording medium as claimed in claim16, wherein the program data is recorded in one of an area which isfirst accessed by the reproduction device when the multilayer opticalrecording medium is loaded, and an area designated by area informationrecorded in the area first accessed by the reproduction device.
 19. Themultilayer optical recording medium as claimed in claim 17, wherein theprogram data is recorded in one of an area which is first accessed bythe reproduction device when the multilayer optical recording medium isloaded, and an area designated by area information recorded in the areafirst accessed by the reproduction device.
 20. The multilayer opticalrecording medium as claimed in claim 16, wherein the program data isrecorded as pre-pits.
 21. The multilayer optical recording medium asclaimed in claim 17, wherein the program data is recorded as pre-pits.22. The multilayer optical recording medium as claimed in claim 18,wherein the program data is recorded as pre-pits.
 23. The multilayeroptical recording medium as claimed in claim 19, wherein the programdata is recorded as pre-pits.